1. Field of the Invention
The present invention relates to an electronic device having an AGC loop, and more particularly to a portable radio device which compensates errors caused by accuracy in manufacturing electronic parts, etc.
2. Description of the Related Art
Up to now, in a portable radio device such as a cordless telephone, etc., the respective circuits in the device are driven by a battery. For that reason, when a porter (user) uses the portable radio device for a long period, a battery voltage drops, thereby coming to an unusable state.
To eliminate the above defect, a technique in which upon detection of the battery voltage that drops lower than a predetermined voltage, the fact that the voltage has dropped is announced to the user, has been disclosed in, for example, Japanese Patent Unexamined Publication No. Hei 4-200140.
According to the disclosure in the publication, there are provided a primary battery and an auxiliary battery, and when a voltage of the primary battery drops, the battery in use is switched from the primary battery to the auxiliary battery while the fact that the voltage has dropped is announced to the user.
However, in the above conventional portable radio device, a predetermined voltage is compared with an output voltage of the battery, and when the output voltage of the battery is lower than the predetermined voltage, an alarm is given to the user. Under this circumstance, for example, if a transmission power depending on the characteristic of a power amplifier is different between the respective devices, that is, if the transmission power relative to the voltage is different between the respective devices, the following problems occur because the same predetermined voltage is set in all the radio devices. There occurs such a disadvantage that in a radio device, the user is alarmed although the device is still in a communicatable state, and in another radio device, the user is not alarmed even though the communication quality is poor.
Also, when the battery in use is switched from the primary battery to the auxiliary battery, the communication quality is improved in a short period. However, the provision of the auxiliary battery makes it difficult to downsize the device.